Scanning probe microscope system including removable probe sensor assembly

ABSTRACT

A scanning force microscope system that employs a laser ( 76 ) and a probe assembly ( 24 ) mounted in a removable probe illuminator assembly ( 22 ), that is mounted to the moving portion of a scanning mechanism. The probe illuminator assembly may be removed from the microscope to permit alignment of said laser beam onto a cantilever ( 30 ) after removal. This prevents damage to, and shortens alignment time of, the microscope during replacement and alignment of the probe assembly. The scanning probe microscope assembly ( 240 ) supports a scanning probe microscope ( 244 ). Scanning probe microscope ( 244 ) holds a removable probe sensor assembly ( 242 ). Removable probe sensor assembly ( 242 ) may be transported and conveniently attached to the adjustment station ( 250 ) where the probe sensor assembly parameters may be observed and adjusted if necessary. The probe sensor assembly ( 242 ) may then be attached to the scanning probe microscope ( 244 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. Application is a divisional application of U.S. applicationSer. No. 09/253,462, filed Feb. 19, 1999, now U.S. Pat. No. 6,138,503,which is a continuation-in-part of application Ser. No. 08/951,365 filedOct. 16, 1997, now U.S. Pat. No. 5,874,669.

BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to the field of scanning probemicroscopes, including those which use light beam detection schemes.

B. Description of the Prior Art

Scanning force microscopes, also referred to as atomic forcemicroscopes, can resolve features of matter to the atomic level, i.e.,determine features measured to an accuracy of + or −0.10 Angstrom.Scanning force microscopes are members of a class of a broader categoryof microscope known as scanning probe microscopes. As is commonly known,scanning probe microscopes use a probe that senses some parameter of asample such as height, or magnetic field strength. A sensor willtypically monitor a parameter of the probe, such as verticaldisplacement. Scanning probe microscopes include scanning tunnelingmicroscopes, scanning force microscopes, scanning capacitancemicroscopes, scanning thermal microscopes, and other type of probemicroscopes, as is well known.

When used to image the topography of a sample, the scanning forcemicroscope uses a finely pointed stylus to interact with a samplesurface. Scanning force microscopes are typically used to measure thetopography of recording media, polished glass, deposited thin films,polished metals and silicon in preparation for integration intosemi-conductors. A scanning mechanism in the microscope creates relativemotion between the stylus and the sample surface. When a measurement ofthe interaction of the stylus and surface is made, the surfacetopography of the sample can be imaged in height as well as in thelateral dimensions. Other classes of probe microscopes may use differenttypes of probes to measure sample features other than topography. Forexample, the interaction of a magnetic probe with the sample may createan image of the magnetic domains of the sample. Scanning tunnelingmicroscopes use a conductor with a sharp point and a small bias voltageto sense a sample surface, which is then used to form an image of chargedensity.

Scanning force microscopes typically have the stylus mountedorthogonally to the longer dimension of a cantilever. A cantilever is alever constrained on one end, with the other end free to move. Thestylus is attached to the free end, and the cantilever will, therefore,deflect, or bend, when forces are applied to the stylus. In forcemicroscopes, the forces acting on the stylus are the result of theinteraction of the stylus with the sample surface. The combination of astylus, cantilever, and inseparable cantilever supporting elements isreferred to as a probe assembly. The cantilever, as used in a scanningforce microscope, typically has a very weak cantilever force constant,and deflects or bends noticeably when forces as small as one nanonewtonare applied to the free end. Typical cantilever force constant valuesfor such cantilevers are in the range of 0.01 N/m to 48N/m, where N isin Newtons and m is in meters. A detection mechanism is operativelyconnected to provide a signal proportional to cantilever deflection.This signal is then processed by a feedback loop to create a feedbacksignal which in turn dives a vertical drive mechanism. The verticaldrive mechanism moves the fixed end of the cantilever toward and awayfrom the sample surface. This vertical drive mechanism maintains thefree end of the cantilever surface at a nearly constant bend angle, asdetected by the detection mechanism, through movement of the probeassembly in proportion to the magnitude of the feedback signal.

During scanning operation, a lateral drive mechanism creates relativelateral motion between the stylus and sample. This relative lateralmotion between the stylus and the surface creates lateral and verticalforces on the stylus as it interacts with surface features passing underthe stylus. The lateral force applies torque to the stylus andcantilever. The vertical force on the stylus causes the cantilever freeend to deflect vertically. The known lateral position of the stylus overthe sample can be expressed in terms of x and y coordinates. Thevertical deflection of the cantilever defines a height or z value. The xand y coordinates create a matrix of z values which describe the surfacetopography of the sample. The scanning mechanism includes of thevertical and lateral drive mechanisms.

In order to detect and quantify the cantilever deflections, a laser beamis directed onto the free end of the cantilever opposite the surfacesupporting the stylus. The surface illuminated by the laser beam is atleast partially reflecting. By measuring the position of the reflectedbeam as the lateral drive mechanism operates, the deflection of the freeend of the cantilever is determined. Preferably, a vertical array of twoconventional light-sensitive devices detects the position of thereflected beam. These devices produce electrical signals that representthe bend angle of the free end of the cantilever. The difference betweenthe two signals created by the two light-sensitive devices is a signalthat is proportional to the displacement of the cantilever deflection inthe vertical direction. Alternatively, and most preferred, by use offour light-sensitive devices in a quadrant array both the cantilevertwist and cantilever vertical deflection can be measured. The verticaldrive mechanism receives signals processed from the vertical componentof the output of the light-sensitive devices.

In probe microscopes, it is often necessary to replace the probeassembly. This may result from a blunted stylus tip typically caused bywear of, or by small particles that adhere to the tip as it scans overthe sample. Also, the stylus or the cantilever, or both can break, thusnecessitating replacement of the probe assembly. When the probe assemblyis replaced, the new cantilever often is not in the same position as theprevious cantilever, relative to the laser and associated optics.Adjustment of either the laser beam angle or the probe assembly positionis then required. Conventional alignment mechanisms restore the beam toits proper position on the reflecting surface of the cantilever.

The initial adjustment of the laser to direct its beam onto thecantilever can be accomplished in various ways. See, for example, U.S.Pat. No. 5,861,550, “Scanning Force Microscope and Method for BeamDetection and Alignment” by Ray, and copending U.S. application Ser. No.09/183,195, now U.S. Pat. No. 6,189,373 by Ray, titled “Scanning ForceMicroscope and Method for Beam Detection, and copending U.S. applicationSer. No. 08/951,365, now U.S. Pat. No. 5,874,669 by Ray titled “ScanningForce Microscope with Removable Probe Illuminator Assembly”.

The manufacture of the probe together with its associated stylus, may beaccomplished with micro-machining, ion beam milling, or other techniquesas are well known. In some instances resulting, the stylus may have animproper shape, such as, for example, an aspect ratio or a nonsymetrythat will prevent its use. When such a stylus is used to scan a samplesurface, the image obtained would be distorted. Thus, before use, astylus must be characterized by first scanning a sample of known surfacefeatures and then comparing the known features with the image obtainedby the stylus. If the stylus has an undesirable shape, the image willnot compare favorably with the known sample features and the stylustypically will be rejected in favor of a stylus that provides afavorably comparable image. For the purpose of the present invention,and as is commonly understood in this field, the above-described processis known as stylus or tip characterization.

Known scanning probe microscopes are shown in U.S. Pat. No. 4,935,634 toHansma et, al, and U.S. Pat. No. 5,144,833 to Amer et, al. These devicesmove the sample laterally and vertically under a stationary stylus whiledetecting the cantilever deflection with the laser beam apparatusdescribed above. These microscopes have a disadvantage stemming from thelimited force capability of the lateral and vertical drive mechanisms.When the sample weight is great compared to the force created by thedrive mechanisms, the sample will then move very slowly or not at allunder the stylus. The mechanical resonance of these scanning mechanismsis also undesirably low with large moving mass.

Other known microscopes, as described in U.S. Pat. No. 5,496,999 toLinker et. al. and U.S. Pat. No. RE 35,514 to Albrecht et. al. haveremovable assemblies comprising laser, cantilever, and adjustmentmechanisms mounted to the fixed reference frame of the microscope base.But, these microscopes also have the disadvantage as described above inthat they move the sample under the stationary stylus. Further, theassemblies are too massive to be mounted to the lateral and verticaldrive mechanisms because they permit adjustment of the beam path orprobe position only while the assembly is mounted to the microscope.

Other known microscopes are described in U.S. Pat. No. 5,481,908, andits continuation, U.S. Pat. No. 5,625,142, to Gamble. These microscopesuse a stationary sample, but move the laser, the cantilever, and all ofthe associated mechanisms necessary to make initial adjustment of thelaser beam. Because the laser moves with the cantilever, the laser beamfollows the motion of the cantilever during scanning. However, therelatively great mass of the moving parts of these microscopes limitsthe rate of image data collection.

Other known microscopes attempt to overcome the disadvantage of movingthe sample by using an interferometric method to track a movingcantilever. These microscopes are described in U.S. Pat. No. 5,025,658,and its continuation, U.S. Pat. No. 5,189,906, to Elings et al. However,this approach suffers from false signals received by the interferometer,as a result of light reflected from the sample surface.

Still other known microscopes use moving beam steering optics with astationary laser source, as described in U.S. Pat. No. 5,524,479, andU.S. Pat. No. 5,388,452, to Harp and Ray; U.S. Pat. No. 5,463,897, andU.S. Pat. No. 5,560,244, to Prater et al.; and in U.S. Pat. No.5,440,920, and U.S. Pat. No. 5,587,523 to Jung et. al. These microscopesemploy a fixed position laser and optical elements that move inconjunction with the moving probe assembly. As a result of the movingoptical elements, the laser beam experiences a refraction such that itmore or less follows the reflecting surface of the moving cantilever.However, these microscopes have noticeable deficiencies when the probeassembly must be replaced, because initial alignment of the laser beamthrough the optics, and onto the newly installed cantilever, aretypically time consuming and tedious. As a result, these microscopes donot readily lend themselves to industrial applications.

With these microscopes, it is possible to place a low mass operatorcontrolled adjustment mechanism on the moving end of the drivemechanisms to reposition the probe assembly rather than aligning thelaser. The probe assembly then can be aligned with the laser beam.However, the vertical and lateral drive mechanisms often consist of thinwalled piezoelectric tubes, and such tubes are quite fragile. Theoperator may apply too much force when adjusting the probe holdingmechanism attached to the tubes thus damaging or breaking the tubesduring the alignment process. Also, this alignment process can also betedious.

Other known attempts to solve this problem, such as described in U.S.Pat. No. 5,496,999, to Linker et al, use precision mounting of the probeassembly on the microscope. By carefully machining the parts to hightolerances, it is possible to bring the probe into near alignment withthe laser light source. This method, however, generally results inhigher costs, and normally still results in the need for a final smalladjustment of the laser beam or probe position.

Still other attempts to solve this problem, as exemplified in U.S. Pat.No. 5,705,814, rely on systems that move the scanning mechanism into aposition relative to the probe assembly using an X, Y translator, a Ztranslator, and an optical system to detect when the scanning mechanismand the to-be-mounted probe assembly are in alignment. This approachthen uses either a vacuum or a mechanical mechanism to capture and holdthe probe assembly. These systems are very complex and expensiverelative to the invention presented in this application.

OBJECTS AND SUMMARY OF THE INVENTION

The scanning probe microscope system, removable probe sensor assembly,scanning force microscope system and removable probe illuminatorassembly have the following objects and advantages over the prior art:

(a) the probe illuminator assembly with prealigned laser and probeassembly can be replaced on the microscope and the microscope is readyfor immediate operation without tedious alignment of the laser or probeassembly;

(b) the laser and probe compose a probe illuminator assembly that isconveniently removable from the vertical and lateral drive mechanisms incase of failure of the laser;

(c) adjustment of the laser beam is accomplished while the probeilluminator assembly is removed from the microscope thereby preventingdamage to the vertical and lateral drive mechanisms during the alignmentprocess;

(d) during scanning the laser beam accurately tracks the motion of theprobe assembly;

(e) the removal and replacement of the probe illuminator assembly can beautomated;

(f) the stylus may be easily characterized prior to mounting to themicroscope;

(g) the removable portion of the microscope may be the probe sensorassembly which is applicable to other classes of probe microscopes;and/or

(h) the separate adjustment station can provide monitoring, adjusting,and aligning mechanisms to calibrate the probe sensor assembly.

The scanning probe microscope system, described below has a removableprobe sensor assembly that may be characterized by a separate adjustmentstation.

Also, the scanning force microscope system described below has a lowmass laser, such as the model SLD 1122VS made by Sony Electronics, Inc.,and a probe assembly mounted in a conveniently removable probeilluminator assembly. The illuminator assembly is connected to themoving portion of the scanning mechanism and is, therefore, in themoving reference frame of the microscope. The laser and probe assemblymove as a unit, and the laser beam unerringly tracks the cantileverduring scanning. When replacing the probe assembly, the operator easilyand conveniently removes the probe illuminator assembly from themicroscope. The illuminator assembly is then replaced with a newprealigned illuminator assembly. Further, the probe assembly may bereplaced in the just removed illuminator assembly and aligned withoutdamage to the microscope scanning mechanism.

The scanning force microscope system, further includes a separateadjustment station and probe sensor assembly transport holders. Thisstation provides for the alignment, and characterization of theremovable probe sensor assembly and its associated components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a scanning force microscope system employing a firstembodiment of the invention in which a removable probe illuminatorassembly is attached to a scanning mechanism by means of a receiverassembly.

FIG. 1A shows the probe assembly of the FIG. 1 embodiment.

FIG. 2 shows the removable probe illuminator assembly of the FIG. 1embodiment.

FIG. 3 shows a second, alternate embodiment of a removable probeilluminator assembly.

FIG. 3A shows the adjustable mirror assembly of the FIG. 3 embodiment.

FIG. 4 shows an alternate embodiment insertion connection.

FIG. 5 shows a third, alternate embodiment of a removable probeilluminator assembly, with an oscillator device and a magnetic sensor.

FIG. 6 shows a fourth, alternate embodiment of a removable probeilluminator assembly, with a stylus in fluid.

FIG. 7 shows a fifth, alternate embodiment of a removable probeilluminator assembly.

FIG. 8 shows a sixth, alternate embodiment of a removable probeilluminator assembly.

FIG. 9 shows a scanning probe microscope system including a microscopeand an adjustment station.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a preferred embodiment of the invention. A microscopeframe 10 supports a lateral driver 12 coupled to a vertical driver 16 bya coupler 14. Vertical driver 16 supports a receiver assembly 18. Aremovable probe illuminator assembly 22 supports a laser 76 with a laserfocusing lens 84 and a probe assembly 24 detailed in FIG. 1A. Probeilluminator assembly 22 is shown in FIG. 2. Laser 76 creates a laserbeam 26. Laser beam 26 reflects off of a cantilever 30, which supports astylus 46, to form a reflected beam 32. Stylus 46 follows the topographyof a sample 28. Reflected beam 32 passes through a beam sizing lens 34and impinges on a first photodiode 38 or a second photodiode 40 or both.A difference amplifier 42 receives the output signals from photodiodes38 and 40. Beam sizing lens 34 is optional and either increases ordecreases the diameter of the beam to a value that matches the lightsensitive areas of photodiodes 38 and 40. The focal lengths andpositions of lenses 84 and 34 are determined, in a conventional fashion,calculated to sufficient accuracy using the thin lens formula:

1/f=1/s+1/s,

where f is the focal length of the lens, s is the object distance to thelens, and s′ is the desired distance from the lens to the image. Theappropriate sign conventions must be followed when making thedeterminations.

FIG. 1A shows probe assembly 24 with a die 50 which supports cantilever30. Cantilever 30 has an upper surface 48 which is at least partiallyreflecting. The cantilever surface opposite surface 48 supports stylus46. Cantilever 30 has a weak spring constant and will deflectmeasurably, i.e., ±10 Angstrom, with as little as one nanonewton offorce applied to stylus 46. Die 50 is attached to a tab 96 with aconventional adhesive (not shown). Tab 96 has a tab alignment hole 104.

FIG. 2 illustrates, in detail, the relationship of vertical driver 16 toreceiver assembly 18 and associated parts. Receiver assembly. 18comprises a receiver 54 with a tapered receiver bore 56 that becomessmaller at its lower end. A receiver ball 58 and a receiver spring 60are held captive in receiver bore 56 by a receiver spring cap 62. Areceiver board 112 has three receiver board leads 116 attached.Conventional laser diode assemblies use an internal photodiode to sensethe output intensity of the internal laser. Such an assembly requiresthree electrical leads. One lead provides current to the laser andanother lead brings out the signal from the photodiode. A third leadprovides a common ground connection for both the laser and thephotodiode. Receiver board 112 is attached flush in a receiver groove 64with adhesive (not shown).

A laser holder 66 has a laser bore 72 which penetrates holder 66 at anangle to its top surface. A laser beam throughbore 74 is smaller thanand coaxial with bore 72 and continues through to the lower surface oflaser holder 66. The top surface of laser holder 66 has a holder groove68 and a detent hole 70. Laser 76 is inserted into laser bore 72. Lens84 may be an integral part of laser 76 or may be mounted in laser holder66. Laser 76 has laser leads 78. Laser leads 78 are attached to a laserboard 80. When laser 76 is inserted into laser bore 72 laser board 80fits flush into a laser board slot 82.

A probe holder 88 has a through slot 90 through which a probe holderscrew 108 is inserted and a probe holder throughbore 92. Probe holderscrew 108 screws into laser holder 66 to hold probe holder 88 onto laserholder 66. Probe holder 88 supports a tab pin 98. A tab clamp 100 clampsprobe assembly 24 to probe holder 88. Probe assembly 24 is positionedsuch that tab pin 98 penetrates tab alignment hole 104, as shown in FIG.1A. A tab clamp screw 102 attaches tab clamp 100 to probe holder 88.

FIG. 3 illustrates an arrangement of an alternate receiver assembly 110which receives a laser assembly 118. Assembly 110 is attached tovertical driver 16 and includes an alternate receiver 114 and a receiververtical board 146 which has receiver board leads 116 to power the laserand convey the photodiode sensor signal. Receiver assembly 110 alsocontains ball 58, spring 60 and cap 62. Laser assembly 118 has a lasermirror probe holder 120. Holder 120 supports laser 76 which in turnsupports a laser vertical board 144 by way of laser leads 78. Holder 120further has a laser throughbore 134 to allow an emitted beam 138 to passthrough holder 120 and impinge on a mirror surface 126. Mirror surface126 is part of a mirror assembly 122, that is shown in detail in FIG.3A. A reflected beam segment 140 reflects from mirror surface 126 andpasses through a mirror throughbore 136. Reflected beam segment 140 thenimpinges on cantilever 30 and reflects a second time to form reflectedbeam 32.

FIG. 3A provides the details of mirror assembly 122. A mirror plate 128has an attached pivot pin 142. A mirror 132 is also attached to plate128 with an adhesive (not shown). An elastic pad 130 is positionedagainst plate 128. Assembly 122 is fastened to laser mirror probe holder120 shown in FIG. 3 by mirror adjustment screws 124.

FIG. 4 shows an insertion and extraction device for attachment anddetachment. A tang receiver 150 has four tangs 152 locatedcircumferentially around tang receiver 150. A flange assembly 154 has acircular flange 156 around its top surface. Tang receiver 150 is made ofa material which provides for elastic displacement of tangs 152, i.e.,bending. As flange assembly 154 is pressed against tang receiver 150,tangs 152 displace slightly in a radial direction, i.e., outwardly asshown in FIG. 4, and then spring back in to capture flange assembly 154.

FIG. 5 shows a third alternate probe illuminator assembly 170 thatsupports a conventional oscillator device 164. Cantilever 30 supportsstylus 46. Stylus 46 may be composed of, or coated with, a conventionalmagnetic sensing material 168. Stylus 46 is disposed on or near sample28.

FIG. 6 shows a fourth alternate probe illuminator assembly 158 withcantilever 30 and a conventional sample and fluid container 162.Container 162 contains a conventional fluid 160 and sample 28.

FIG. 7 shows a fifth alternate embodiment of a removable probeilluminator assembly 196 in which a fixed receiver 180 is attached tovertical drive 16 typically with an adhesive (not shown). A secondalternate receiver assembly 182 is attached to fixed receiver 180 byclamping second alternate receiver assembly 182 to fixed receiver 180with a clamp screw 186. Second alternate receiver assembly 182 includesan adjustable receiver 184, spring contacts 188, electrical power leads,two of which are shown at 190, receiver pins 192 and an elastic pressurering 194. The elastic pressure ring 194 is a conventional O-ring that ischosen for proper size and elastic properties, i.e., to provide arestoring force to the assembly. The most preferred type is silicon,with viton, and polyurethane O-rings also preferred. The restorativeforce also may be supplemented with, or supplied entirely by the springcontacts.

The fifth alternate removable probe illuminator assembly 196 is capturedby second alternate receiver assembly 182.

Fifth alternate removable probe illuminator assembly 196 mounts aninsulator plate 198 with two arcuate electrical contacts 200 andcontains grooves 204. Fifth illuminator assembly 196 also has a mountedviewing lens 202, laser 76 with laser leads two of which are shown at78, mirror 132, and probe assembly 24 with cantilever 30. Sample 28 ispositioned such that cantilever 30 may scan sample 28.

FIG. 8 shows a sixth alternate embodiment of a removable probeilluminator assembly in which a third alternate receiver assembly 214 isattached to vertical driver 16, typically with an adhesive (not shown).Third alternate receiver assembly 214 contains four clips 216 (onlythree are shown) which are connected to conductor traces 218. Electricalpower leads 190 are attached to conductor traces 218 typically withsolder (not shown). The sixth alternate removable probe illuminatorassembly 222 is captured by third alternate receiver assembly 214. Sixthalternate removable probe illuminator assembly 222 contains four pins220, laser 76 with leads 78 connected electrically to two of pins 220,mirror 132, and probe assembly 24 with cantilever 30. Sample 28 ispositioned such that cantilever 30 may scan sample 28.

FIG. 9 shows a scanning probe microscope system 238 including amicroscope assembly and an adjustment station. Scanning probe microscopeassembly 240 contains a scanning probe microscope 244 with a removableprobe sensor assembly 242. Removable probe sensor assembly 242 includesa removable probe assembly, as discussed above for example withreference to FIGS. 7 and 8, but not shown in FIG. 9. As will beappreciated by those skilled in this field, the sensor assembly need notinclude a cantilever, but could include other sensing components.Removable probe sensor assembly holders 254 are shown holding removableprobe sensor assemblies 242 for transport to and from adjustment stationassembly 248 which holds removable probe sensor assembly 242 andcalibrated, characterized sample 252.

Operation of the Invention

The operation of the present scanning force microscope system will bedescribed with reference to FIG. 1. Lateral driver 12 is fixed at theupper end to microscope frame 10, but its lower end can move laterally.All parts attached to the lower end appear to pivot about a pointapproximately at the midpoint along the length of lateral driver 12.Consequently, coupler 14, vertical driver 16, receiver assembly 18, andremovable probe illuminator assembly 22 move laterally. Stylus 46therefore, moves laterally across the surface of sample 28.

Laser 76 also moves laterally and directs laser beam 26 at cantilever30. Because laser 76 is in the same moving frame of reference ascantilever 30, laser beam 26 constantly follows the movement ofcantilever 30. Focusing lens 84 focuses beam 26 to an approximate pointon cantilever 30.

As Stylus 46 encounters changing topography, with typical ranges ofvertical motion up to seven microns, and in some applications, up to tenmicrons, during its lateral scan it applies force to cantilever 30causing minute deflections of cantilever 30. The deflections causereflected beam 32 to change direction and impinge at different locationson photodiodes 38 and 40 changing their electrical outputs. Conventionaldifference amplifier 42 then outputs the changes. Difference amplifier42 output is routed to a conventional feedback signal processor (notshown) and then to conventional vertical driver 16. Vertical driver 16then expands and contracts along its length in response to the processedelectrical signals thus causing the deflection of cantilever 30 toreturn to its preset position. Beam sizing lens 34 is optional andincreases or decreases the spot size of the beam to a value that matchesthe size of photodiodes 38 and 40 as necessary.

In accordance with the present invention, each illuminator assembly. 22is adapted and configured so that its location and angular position issubstantially the same as in each preceding and each succeedingassembly. Illuminator assembly 22 may be removed with slight rotationalmoment or tensile force or both without tools or danger of damage toother parts of the microscope. Thus the current invention results infast removal and secure and accurate installation of probe illuminatorassembly 22.

When probe assembly 24 is replaced, the new probe assembly must beinstalled in precise alignment with laser 76. Because probe illuminatorassembly 22 is fast, accurately and securely removable from receiverassembly 18 the alignment may be accomplished with assembly 22 removedfrom the entire microscope. Because the probe illuminator assembly isremoved from the microscope, alignment of the beam in its x-y plane maybe facilitated by conventional jigs and tools as known in this field.Complete illuminator assemblies are relatively inexpensive, and when oneis removed it may be replaced from a set of prepared illuminatorassemblies that have already been aligned. The removed assembly may thenbe recycled and refitted with a new probe assembly as described above.

Referring to FIG. 2, the operation of receiver assembly 18 and removableprobe illuminator assembly 22 will be described. Assembly 22 containslaser holder 66. Laser holder 66 slides laterally into receiver 54. Whenholder 66 is in position in receiver 54, the force from receiver spring60 presses receiver ball 58 into detent hole 70. Laser holder 66 is thenheld gently but firmly to receiver 54. A slight lateral force in adirection along the axis of laser holder groove 68 will release assembly22 from receiver assembly 18. Laser board 80 and receiver board 112 makeelectrical contact and provide power to laser 76 via laser leads 78 andreceiver board leads 116.

In order to provide precise alignment of laser 76 and probe assembly 24,assembly 24 is mounted to probe holder 88 by way of probe holder screw108 and slot 90. By loosening screw 108 probe holder 88 moves laterallywith reference to laser holder 66 in the direction of slot 90 and pivotsaround screw 108. This procedure is accomplished while assembly 22 isremoved from the microscope.

Probe assembly 24 is conveniently removed from probe holder 88 byapplying slight pressure to tab 100 and slipping probe assembly 24 offtab pin 98.

With reference to FIG. 3, the operation of alternate removable probeilluminator assembly will be explained. Holder 120 slides laterally intoalternate receiver assembly 110 in much the same manner as in FIG. 2,except that holder 120 slides into receiver assembly 110 from left toright. Again, receiver ball 58 presses into detent hole 70 allowinglaser assembly 118 to be installed and removed with slight lateralpressure.

In this alternate assembly, laser 76 is aligned in a lateral direction,such that emitted beam 138 impinges on mirror surface 126, and resultsin reflected beam segment 140. The angle of mirror surface 126 can bechanged to redirect beam segment 140 onto cantilever 30 as in FIG. 3.

A source of electrical power (not shown) is connected to receiver boardleads 116. As assembly 118 slides into receiver assembly 110 laservertical board 144 presses against receiver vertical board 146 makingelectrical contact between laser leads 78 and receiver board leads 116.This connection provides electrical power to laser 76.

With reference to FIG. 3A, adjustment of the angle of mirror surface 126will be described. Elastic pad 130 is sandwiched between mirror plate128 and holder 120. Mirror plate 128 compresses elastic pad 130 whenscrews 124 are tightened. Consequently, mirror 132 will rotate about thepoint where the end of pivot pin 142 and holder 120 meet.

Referring to FIG. 5, oscillator device 164 causes stylus 46 to vibrateand periodically approach and withdraw from sample 28 in a conventionalmanner. Magnetic sensing material 168 senses any magnetic fieldsemanating from sample 28. The interaction of sensing material 168 andany magnetic fields from sample 28 causes cantilever 30 to deflectmagnetic material 168 is, therefore, a magnetic sensing device.Alternately, 168 may be a conventional capacitance sensing device, athermal sensing device, or a photon sensing device all of which areconventional and known to the art.

Referring to FIG. 6, sample 28 is submersed in conventional fluid 160.Both sample 28 and fluid 160 are contained in fluid container 162.Alternate probe illuminator assembly 158 is positioned such thatcantilever 30 and stylus 46 are submersed in fluid 160 in a conventionalmanner.

Referring to FIG. 7, the free end of vertical drive 16 has fixedreceiver 180 attached with an adhesive. Receiver assembly 182 can thenbe adjusted either in rotation or in the vertical direction or bothbefore being clamped to fixed receiver 180. Fifth alternate removableprobe illuminator assembly 196 is removably captured by receiverassembly 182 with a bayonet connection, i.e., by aligning grooves 204with pins 192, inserting assembly 196 onto receiver 182 and rotatingassembly 196 to a detent position. Elastic pressure ring 194 deformsagainst the interior of assembly 196 and applies force on pins 192 tohold assembly 196 and receiver 182 together. Alternate spring 260 isused in lieu of elastic pressure ring 194 to force pins 192 against theinterior of assembly 196. This positions assembly 196 and receiver 182relative to each other.

Spring contacts 188 bend and are forced against arcuate contacts 200.Thus electrical current may now flow through electrical power leads 190,spring contacts 188, arcuate contacts 200, and laser leads 78 to powerlaser 76. Laser 76 produces a light beam (not shown) which is reflectedoff mirror 132 and onto cantilever 30.

A viewing lens 202 is mounted in a convenient location in removableprobe illuminator assembly 196 and is used to make optical observationsof either cantilever 30 or sample 28 or both.

Referring to FIG. 8, the free end of vertical drive 16 has thirdalternate receiver assembly 214 attached with an adhesive (not shown).Sixth alternate removable probe illuminator assembly 222 is rotated suchthat conventional pins 220 are aligned with conventional clips 216.Assembly 222 is then moved against receiver assembly 214 such that pins220 penetrate clips 216 and illuminator assembly 222 is captured byreceiver assembly 214 and held in place by frictional forces betweenpins 220 and clips 216. Clips 216 are electrically connected toelectrical power leads 190 by conductor traces 218. Clips 216 makeelectrical contact with pins 220 which are in turn electricallyconnected to laser leads 78. Thus electrical current may flow throughpower leads 190, traces 218, pins 220 and leads 78 to power laser 76.Laser 76 produces a light beam (not shown) which is reflected off mirror132 and onto cantilever 30.

Alternate viewing support tube 210 supports viewing lens 212 and isinserted through vertical driver 16, third alternate receiver assembly214 and into sixth alternate removable probe illuminator assembly 222.In this way viewing lens 212 is placed in position to visually observeeither cantilever 30 or sample 28 or both.

Referring to FIG. 9, scanning probe microscope assembly 240 supportsscanning probe microscope 244. Removable probe sensor assembly 242typically includes a housing made of lightweight material such asaluminum or plastic. The housing of assembly 242 is often shaped in theform of a cylinder, typically with a diameters of less than 30millimeters and with a pylon to capture and hold a probe assembly in aposition that allows the probe unrestricted access to a sample surface.Removable probe sensor assembly 242 may be removed or attached tomicroscope 244 with any of the methods described earlier. Probe sensorassembly 242 may be removed for renovation, repair, calibration, orreplacement with a new assembly 242. Removed assemblies 242 may then beplaced in removable probe sensor assembly holder 254. Holder 254 is thenuse to transport sensor assemblies 242 to adjustment station 250 wheresensor assemblies 242 may be mounted to station 250 and repaired orcalibrated. After either new or reconditioned sensor assemblies 242 havebeen deemed acceptable for use they may then be transported to scanningprobe microscope 244 either singly or in groups in holder 254 forattachment to microscope 244.

Removable probe sensor assembly 242 may include a laser (not shown), acantilever (not shown), and optical devices (not shown). Thesecomponents may be configured in any of the embodiments described earlierand to form removable probe illuminator assembly 22 (shown in FIG. 1)for a scanning force microscope. However, removable probe sensorassembly 242 may alternately include a pointed conductor (not shown) toform a removable probe sensor assembly 242 for a scanning tunnelingmicroscope, for example, other alternate embodiments of the removableprobe sensor assembly 242 may include a thermal sensor 262, acapacitance sensor 264, a magnetic sensor 266, or a near-field photonsensor 268 (not shown). The thermal, capacitance, magnetic field, andphoton sensors 262, 264, 266, and 268 are conventional and well known inthe art. Thermal sensors may use thermocouples, thermal sensitiveresistance elements or thermal sensitive semiconductor elements. As isknown, near-field scanning microscopes may use photon sensors andemitters coupled to optical fibers or other transparent plastics andglasses that may be drawn or tapered into small solid or hollow points.In each of these embodiments of a scanning probe microscope, variousconventional support devices, including miniaturized electronic supportcircuits, signal generators, or photon generators (not shown) may beincluded in the removable probe sensor assembly 242. The inventiondescribed here permits replacement and realignment of the constituentparts of removable probe sensor assembly 242 to be accomplished offline, at adjustment station 248, thus allowing scanning probe microscope244 to continue in service while spare, removable probe sensorassemblies 242 are under repair or realignment at station 248.

Adjustment module 250 may contain either laser or incandescent lightsources. Adjustment module 250 may contain a variety of circuitsincluding amplifiers, analog to digital converters, digital to analogconverters, and amplitude and phase detection circuits (not shown). Suchcircuits may further contain electronic and sensing devices includingphotodiode or phototransistor receivers (not shown) for detecting anddetermining the reflected angle and intensity of any light emanatingfrom assembly 242. In addition, adjustment module 250 may includemechanical devices such as gear assemblies, rotary or linear motors,piezoelectric, electrostrictive, or electromagnetic devices (all notshown) for the actual adjustment of assemblies 242 or to create rastermotion of assemblies 242 over calibrated sample 252. Any probecomponents that are part of assembly 242 may be characterized resultingin the rejection or acceptance of assembly 242.

Advantages of the Present Invention

The scanning force microscope system of the present invention permitsattachment of the probe illuminator assembly to the moving portion ofthe scanning mechanism and provides easy installation on, and removalfrom, the microscope. The cantilever can then be replaced on the removedassembly without damaging, stressing, or contaminating the lateral orvertical drive mechanisms. The laser beam can also be convenientlyaligned while the assembly is removed from the microscope therebyavoiding damage to the lateral or vertical drive mechanisms. Afterinstallation of the prealigned probe illuminator assembly on themicroscope, the light beam accurately tracks the motion of thecantilever as it scans over the surface of the sample. Further, the useof low mass components in the probe illuminator assembly reduces themass of the moving elements, enabling the system to scan at a fasterrate.

The connection mechanism for the probe illuminator assembly may be madeas shown above using a lateral or vertical slide connection andoperation. Connection may also be made by lateral or vertical insertionor by a combination of sliding and rotating or insertion and rotation.

The scanning mechanism can take many forms. The vertical and lateraldrivers can be piezoelectric blocks, stacks, tubes, bimorphs, orflexures. Piezoelectric devices can actuate the vertical and lateraldrivers. Magnetic or magnetostrictive devices can also be used as suchdrivers. The vertical and lateral drivers can be combined into a singlepiezoelectric tube which can create relative motion in the x, y, and zdirection with respect to the sample surface.

The light source can be a laser, a light emitting diode, or anincandescent source. The examples show the reflected beam locationdetectors as photodiodes, but other types of known devices that candetect light may be used in the present invention. For example, thelight detecting devices can be phototransistors. If an array of four ormore light detecting devices is employed, the lateral motion of the beamas well as the vertical motion can be determined.

It is possible to mount a detector array of photodiodes in the removableprobe illuminator assembly. Light weight detector arrays such as theCentrovision, Inc. (Newbury Park, Calif.) QD7-0 quad photodiode aresuitable for such mounting. These associated light sensitive devices, asmounted to the probe illuminator, receive the light beam reflected fromthe cantilever during operation. The probe assembly may then be removedfrom the microscope to facilitate adjustment of the position of thelight beam, such that there is no need for alignment of a fixed detectorassembly after installation of the probe illuminator assembly into themicroscope. This arrangement also eliminates the slight error in thedetector signal caused by relative lateral movement between the detectorand the fixed probe illuminator assembly. The added detector array wouldslightly increase the mass of the moving portion of the microscope, butnot enough to degrade operation. Electrical signals for detectorsmounted in the removable probe illuminator assembly can be routedthrough contacts similar to those described for providing electricalpower to the light source, as will be understood by one of ordinaryskill in this field.

The scanning force microscope system of the present invention canoperate with the sample submerged in fluids. Further, the microscope canoperate by oscillating the cantilever and detecting some parameter ofthe oscillation such as the amplitude, frequency, or phase change. Theoscillating cantilever may actually come into intermittent contact withthe sample surface.

In the examples, a stylus creates a bending action of the cantilever.However, other types of probes, such as magnetic probes, can bend thecantilever.

Many types of scanning probe microscopes can be constructed such thatthe probe and associated detection features of the present invention canbe incorporated. In such microscopes, an assembly of the presentinvention may need either to be calibrated or modified or both, withoutdeparting from the inventive features of the present invention, as willbe understood by one skilled in this art. The scanning probe microscopesystem for probe sensor assembly removal and characterization, of thepresent invention, may be used with various types of microscopes withinthe field of the invention.

Thus, the scope of the invention is to be determined by the appendedclaims, and their legal equivalents, rather than by the examples given.

I claim:
 1. A scanning probe microscope for creating an image of asample comprising: (a) scanning means, (b) stylus characterizationmeans, and (c) a plurality of removable probe illuminator assemblieseach comprising a light source and at least one of said assembliescomprising a stylus, said assemblies being removably attachable to saidscanning means and said stylus having been characterized prior toattachment of said assembly to said microscope, whereby said assembliesmay be replace one after the other on said microscope insuring that theinitial scan result of said microscope, after attachment of saidassembly comprising said characterized stylus, is free of distortionfrom possible defects in said stylus.
 2. The microscope of claim 1wherein at least one of the removable probe assemblies further comprisemagnetic field sensing means.
 3. The microscope of claim 1 wherein atleast one of the removable probe assemblies further comprise capacitancesensing means.
 4. The microscope of claim 1 wherein at least one of theremovable probe assemblies further comprise thermal sensing means. 5.The microscope of claim 1 wherein at least one of the removable probeassemblies further comprise photon sensing means.
 6. The microscope ofclaim 1 wherein at least one of the removable probe assemblies furthercomprise oscillation means adapted to oscillate a probe assembly.
 7. Themicroscope of claim 1 wherein at least one of the removable probeassemblies comprises at least one lens to permit optical observation ofeither a probe or a sample to be observed.
 8. The microscope of claim 1comprising electrical contacts positioned on said microscope adapted tomake electrical contact with contacts positioned on said removable probeassemblies.
 9. A scanning probe microscope for imaging a samplecomprising: (a) scanning means, and (b) a plurality of removable probeassemblies at least one of which comprises a light source and a probe,and adjusting means for steering the light from said light source suchthat said light from said source is brought to a predisposed positionrelative to said probe before said assembly has been mounted to saidmicroscope, said assemblies being removably attachable to said scanningmeans, whereby said assemblies may be replace one after the other onsaid microscope insuring that the initial scan result, after placementof said at least one assembly on said microscope, is free of defectscaused by misalignment of said light and said probe.
 10. The microscopeof claim 9 wherein at least one of the removable probe assembliesfurther comprise magnetic field sensing means.
 11. The microscope ofclaim 9 wherein at least one of the removable probe assemblies furthercomprise capacitance sensing means.
 12. The microscope of claim 9wherein at least one of the removable probe assemblies further comprisethermal sensing means.
 13. The microscope of claim 9 wherein at leastone of the removable probe assemblies further comprise photon sensingmeans.
 14. The microscope of claim 9 wherein at least one of theremovable probe assemblies further comprise oscillation means adapted tooscillate a probe assembly.
 15. The microscope of claim 9 wherein atleast one of the removable probe assemblies comprises at least one lensto permit optical observation of either a probe or a sample to beobserved.
 16. The microscope of claim 9 comprising electrical contactspositioned on said microscope adapted to make electrical contact withcontacts positioned on said removable probe assembly.
 17. A probeassembly for use in a scanning probe microscope comprising: (a) acharacterized stylus, (b) a probe, (c) a light source, and (a) adjustingmeans for steering the light from said light source such that said lightfrom said source is brought to a predisposed position relative to saidprobe before said assembly has been mounted to said microscope, wherebysaid assembly may be mounted to said microscope insuring that theinitial scan results of said microscope are free from distortionresulting from a defective stylus or from incorrectly positioned lightfrom said light source.